The efficiency of gas turbines can depend substantially on the temperature of hot gas that expands in a turbine while performing work. In order to increase efficiency, components (guide vanes, moving blades, heat accumulating segments etc.) exposed to the hot gas can be produced from heat resistant materials and can be cooled as effectively as possible during operation. Different methods have been developed in relation to the cooling of blades, and these can be used alternatively or cumulatively.
One known method includes conducting a coolant, such as pressurized cooling air from the compressor of the gas turbine, in cooling ducts through an interior of the blades. This coolant is allowed to enter into the cooling duct through cooling bores arranged in a distributed fashion. The cooling ducts can be repeatedly reversed in the interior of the blade in a serpentine fashion. See, for example, WO A1 2005/068783. The heat transfer between the coolant and walls of the blade can be improved in this case by additional turbulence generated in the coolant flow by suitable cooling elements, for example turbulators, or impingement cooling. However, complementary methods can permit the coolant to emerge from the interior of the blade such that there is formed on the blade surface a film of coolant, known as film cooling, that provides the blades additional protection against thermal loads.
Particular attention can be paid to the cooling of a narrow trailing edge of the blade. It can be advantageous for the efficiency of the turbine if the trailing edge can be designed to be as thin as possible. The trailing edge should be adequately cooled. Moreover, it can be advantageous to have cooling that is uniform in all operating states. It can be advantageous that the use of coolant be restricted to what is required in order not to exert a disadvantageous influence on the efficiency of the machine.